TARAPUR (Maharashtra): The country's second totally indigenous 540 MWe nuclear power reactor, Unit-3 of the Tarapur Atomic Power Project (TAPP), attained criticality here on Sunday, starting self-sustaining nuclear fission chain reaction in the reactor core.

Nuclear engineers gave commands to instruments in the fully computerised control room of the unit to inject more neutrons to raise their counts from 6,000 to 22,000 concentration. The graph on the display was charting rather erratic upward movement but that alarmed nobody for the top scientists and engineers knew that some neutrons were getting absorbed in strong absorbents.

A few minutes later, at 10.44 a.m., reactor physicists declared criticality as smiles broke on the faces of the country's nuclear family, including Atomic Energy Commission Chairman Anil Kakodkar and Mr. S.K. Jain, Chairman and Managing Director of the Nuclear Power Corporation of India Ltd (NPCIL), the public sector company that designs and builds nuclear power plants.

More than copybook

"This is a great moment," exclaimed Dr. Kakodkar. "Last year, when the first reactor, Unit-4, had attained copybook criticality, it was too smooth, but today it even exceeds that," he said congratulating all concerned.

Mr. Jain said the commercial generation of electricity would commence from July next. The Unit-4, the elder twin, attained criticality on March 6 last year and started commercial power generation on September 12. The TAPP-3&4 together have an installed capacity of 1,080 MWe as against earlier two boiling water type reactors of 160 MWe each. Thus the total capacity of the TAPP rises to 1,400 MWe.

The TAPP-3&4 are of pressurised heavy water reactors (PHWR) design, the mainstay of the nuclear power programme so far. They use natural uranium fuel and heavy water as moderator as well as coolant.

Dr. Kakodkar and Mr. Jain told a press conference after a ceremony of signing the logbook of the Unit-3's Control Room, that the original cost estimate for the twin-unit project was Rs. 8,000 crore but after the NPCIL's `value engineering,' it got reduced considerably.

Early completion

He attributed the savings to early completion of the project. "The project's 70 per cent cost is met out of borrowed capital and the saving in time resulted in the saving of interest to the extent of Rs. 400 crore," he said.

This is going to reflect in the power tariff. Mr. Jain said that earlier it was envisaged that the NPCIL would be able to supply power at the rate of Rs. 4.35 a unit but now they would charge Rs. 2.65 and they would attempt to reduce even this rate to Rs. 2.50.

While Maharashtra would get 38 per cent or 430 MWe share from the new reactors, the rest goes to Gujarat, Madhya Pradesh, Chhattisgarh, Goa and Union Territory of Dadra and Nagar Haveli.

16th power reactor

The TAPP-3 is the 16th nuclear power reactor of India. The other PHWR reactors are of 220 MWe. The scale upto 540 MWe is quite an achievement and the NPCIL has planned to go for 700 MWe reactors at just five per cent additional capital cost. Four such bigger reactors are on the cards, two at Rawatbhata in Rajasthan and two at Kakrapar in Gujarat.

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